1. Field of the Invention
The present invention relates to a surface mount electronic component to be mounted on a printed circuit board or hybrid IC (HIC).
2. Description of the Related Art
Many types of surface mount electronic components are mounted on circuits in electronic apparatus such as personal computers and portable telephones. Known surface mount electronic components include thin film type electronic components formed using thin film forming techniques. A thin film type electronic component has a lead-out electrode which is exposed on an outer surface that is different from a mounting surface and an external electrode which is formed on the outer surface in electrical connection to the lead-out electrode. The lead-out electrode is electrically connected to the external electrode through an exposed part thereof that is exposed on the outer surface. In order to maintain sufficient electrical connection between the lead-out electrode and the external electrode, the lead-out electrode is formed by stacking a plurality of metal thin films to provide the exposed part with a great surface area.
For example, according to a method of manufacturing thin film type electronic components in the related art, a multiplicity of elements such as a lead-out electrode having a multi-layer structure, a plurality of metal thin films constituting circuit elements, and insulation films providing insulation between the metal thin films are formed on a wafer using thin film forming techniques. Then, a protective film for protecting the lead-out electrode, metal film films, and insulation films is formed throughout the wafer to terminate the thin film forming step. Next, the wafer is cut and divided into individual chips. External electrodes are then formed in electrical connection with the lead-out electrodes exposed on the cut surfaces to complete the electronic components. Patent Document 1 discloses a common mode choke coil formed using such a method of manufacturing thin film type electronic components.
Patent Document 1: JP-A-2005-79323
FIG. 5 is a schematic view of a section of a thin film type electronic component 21 according to the related art taken immediately after the component is cut and divided into a chip, the figure showing the neighborhood of a lead-out electrode 25. As shown in FIG. 5, the lead-out electrode 25 is formed on a substrate 3. The lead-out electrode 25 includes a first electrode 25a which has an exposed part exposed on an outer surface (a side surface of the electronic component 21) and a second electrode 25b which has an exposed part exposed on the side surface of the component 21 and having substantially the same electrode width as that of the first electrode 25a and which is formed directly above the first electrode 25a in electrical connection with the first electrode 25a. The term “electrode width” means the length of each of the exposed parts of the first and the second electrodes 25a and 25b in a direction parallel to the contact surface between the first electrode 25a and the second electrode 25b. A protective layer 9 formed from alumina (Al2O3) is formed throughout the wafer to protect the lead-out electrode 25. Therefore, the protective film 9 must stay directly above the lead-out electrode 25 after the wafer is cut into chips. However, when the wafer is cut and divided into chips, a protective layer 9′ on the lead-out electrode 25 may be completely peeled off as indicated by the broken line in FIG. 5. Otherwise, the protective layer 9′ directly above the lead-out electrode 25 may be partially peeled off or damaged instead of being completely peeled off.
The protective layer 9 is formed to improve the reliability of the electronic component 21 in terms of heat resistance and pressure resistance. Therefore, when the protective layer 9′ directly above the lead-out electrode 25 is peeled off, the reliability of the electronic component 21 is significantly reduced, and the product can no longer satisfy predetermined specifications for the same. The yield of manufacture of such electronic components 21 is therefore reduced, and a problem arises in that the manufacturing cost and the cost of the electronic components itself is increased.